Nights at the round table

Wearing snakeskin from head to toe, Dave "Devilfish" Ulliott claims he does not need to train for long nights. He is Britain's highest-earning poker player, one of the game's bad boys, who spent his 21st birthday in prison and has since gained a reptilian reputation on the hard-living professional circuit.

Wearing snakeskin from head to toe, Dave "Devilfish" Ulliott claims he does not need to train for long nights. He is Britain's highest-earning poker player, one of the game's bad boys, who spent his 21st birthday in prison and has since gained a reptilian reputation on the hard-living professional circuit.

Ulliot claims that "marathon sex sessions" are all the preparation he needs to stay awake during tournaments, where players compete in late-night games, day in, day out for weeks on end. He gestures to his young girlfriend. "I can make love for four or five hours. I like to get a woman and ring her out like a flannel." She smiles toothily. Or maybe it's a deep, deep grimace.

Not every card playeer boasts such "mojo," though. On Thursday, the world's best poker players will descend on London for the World Series of Poker Europe. Devilfish's rivals will do everything from pumping iron to meditating in preparation for the tournament, with profound health implications.

Like any pastime, poker can improve your mental and physical wellbeing. But only so long as players pursue their preparations in moderation: sustained sleep deprivation causes complications later in life. Some players cut their razor sharp teeth on the "cash circuit", competing for hard currency in an environment where it isn't uncommon to stay up for two or three days at a time. The World Series, however, is likely to be less harmful, as long as the players are sensible; it will include games starting at 2pm, even if they do last up to 14 hours.

In this week's championship, winners will be awarded three coveted "bracelets" after three different tournaments that culminate with the "main event": a seven-day, £10,000 no-limit Texas hold 'em championship. Here, around 750 gnarled members of the poker fraternity will be whittled down to just one lucky winner who will scoop the jackpot, likely to be around £1.5m. No one wants to be the one who drops off to lose a crucial hand; misinterprets a "tell"; or folds when they should have stuck.

Dr Chris Idzikowski of the Edinburgh Sleep Centre says that as the run of nights wear on in the Texas hold 'em, the players will have to contend with heightened risk-taking and increased suggestibility brought on by a lack of sleep. "Laboratory studies have tended to use card-playing games to demonstrate that people who are sleep-deprived are more likely to make a risky bid, or to be led," he says.

When the money involved can run into the millions – Devilfish has taken almost $5m (£2.5m) from poker tournaments to date – the stakes can turn stratospheric. According to Idzikowski, 4am is the time at which competitors are at their most vulnerable. While everyone needs to find their own solution; Idzikowski suggests indulging in regular physical exercise.

One key horn-blower for physical fitness levels is Annie Duke, one of the world's most successful female players. She says: "For the most part, the top players tend to be people who work out a lot. Playing long hours for five weeks is exhausting. If your body is in good shape, your mind is less likely to falter."

Duke says she notices the difference in her poker performances when she isn't working out, and emphasises "mental work-outs" to help her overcome her fears. On her website she describes how she used to become tearful when she lost a lot of money. Now, she claims she has learnt becoming "unhinged" detrimentally affected her chances in the subsequent rounds. "So I learned to lose at poker."

Another leading player who has had his fill of dealing with a lack of sleep is Phil Hellmuth, who holds the record for the most bracelets won during a world series. Once, when playing in Wales, he claims not to have slept for the 36 hours prior to a tournament. Confronted with two hours off, he went to the gym, "had a really hard work out", and nailed his games.

Hellmuth, however, is used to lack of sleep: he has just been diagnosed with sleep apnoea, a sleeping disorder caused by shortness of breath that means he can wake up six times an hour during the night. "I have been dealing with fatigue for many years," he says.

Beyond this, one of the major problems that US-based players such as Hellmuth will have to contend with is adjusting their body clocks to a different time zone. World Series spokesman Ty Stewart says: "Home-team advantage exists, even in poker. The Americans may find that out the first time they are faced with a decision for all their chips. The drain of international travel, and the bustle of London may sway the outcome. There are no second chances when you're all in. A shot at history, at fame and fortune can be gone in a moment if you lose your wits."

Victoria Coren, the journalist and winner of last year's European Poker Tour, thinks that many of the young men involved in the game like to brag about being physically fit because they do not like to admit they are spending their lives simply sitting around. "There's something child-like about poker; about being able to stay up late. You're kept awake by adrenaline, the thrill, the risk," she says.

Coren reports having more of a problem getting to sleep after an exciting game than staying awake during it, such is the adrenaline pumping through her veins. Despite wistful stories to the contrary, she says that players do not take drugs.

"Nobody will take anything at a serious level," she continues. "People wouldn't use cocaine because it gives you a sense of importance and it's hard to make judgments. You need to keep a clear head. The healthier and more respectable the game becomes, the better. Although it's possibly less poetic."

Dr Idzikowski believes there are no long-term health risks from staying up for sustained periods. He says that the main downsides are associated with heart and stomach problems, stemming from eating at bizarre times of the day, but other than this, players are safe as long as they rest well between games.

Devilfish, meanwhile, walks out of The Independent's canteen where he has just been speaking, holding a 30p banana loosely in his hand like a revolver.

"I nicked this, is that OK?" he asks in his Las Vegas-flecked Hull drawl, looking into the middle distance. There is no end to the man's gall. But even he, when not conducting minor acts of larceny, has confessed to the odd meditative interlude, after coming into possession of a Paul McKenna hypnotism tape.

Apparently, the tape allows him to drift into a trance when he feels sleepy. Maybe there is a soft side to the Fish after all. Does he follow the same routine before every game? He points to his lady once again. "I try and get inside their heads and see what turns them on." The Devilfish, ever the card, has spoken.